Lightning arrester



Patented May 27,1941

LIGHTNING aRREs'rEn Herman B. Wolf, Charlotte, N. C., assigner to General Electric Company, a corporation of New York Application December 13, 1939, Serial No. 309,019

3 Claims.

This invention relates to electric protective devices, and more particularly to devices of this character known as lightning arresters and designed primarily for the protection of electrical equipment from damage `by lightning discharges or other abnormal potentials.

'I'his invention is in thenature of an improvement over the construction shown in my prior Patent No. 1,960,653, issued May 29, 1934. The lightning arrester is of the type having a pair of spaced electrodes with a cylindrical liber tube arranged therebetween. Initially, a small amount of conductive powder adhering to the inner side walls Vof the tube provides a relatively low resistance path for the vdischarge between the spaced electrodes. The flow of dynamic current following the ionization of the gap immediately vaporizes the conducting powder adhering to the tube wall which vapor is expelled together with the gas formed by the disintegration of a portion of the liber tube. For reconditioning the lightning arrester for a subsequent operation, a reservoir of conductive powder is provided in the upper end of the structure together with valve means automatically operable by the increased pressure created by the arc gap, which valve operates to drop a small portion of powder down through the tube after the pressure therein has decreased indicating that the arc has been extinguished. In passing through the tube, the powder coats the side walls and the arrester is in readiness for a subsequent discharge.

Under severe operating conditions, such as prevail in connection with very high voltage power circuits, the correspondingly high discharge currents liowi'ng through the arrester give rise to exceedingly high pressures and temperatures. Such pressures acting upon the valve of the arrester device may cause injury thereto, While the high temperature of the gas forcing past the valve into the reservoir may cause the ignition of the powder stored therein. It is a general object of this invention, therefore, to provide a new and improved lightning arrester of the type referred to having an extremely high current carrying capacity.

It is a more specific object of this invention to provide a new and improved lightning arrester of the general type described that is capable of withstanding extreme conditions of temperature and pressure as may occur upon a heavy current flow therethrough from the line to ground.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto taken in connection with the accompanying drawing,

Fig. 1 is an elevational view illustrating one application of a lightning arrester constructed in accordance with the present invention; Fig. 2 is a sectional view of an embodiment of the invention; Fig. 3 is a fragmentary sectional view illustrating one detail of the construction; Fig. 4 is an enlarged sectional view of one portion of the arrester; and Fig. 5 is a top view of the portion shown in Fig. 4.

With reference to Fig. 1 of the drawing, the lightning arrester is illustrated in a typical installation for protecting a power line from lightning surges. The transmission line or bus bar I0 is suspended by insulators II from asuitable supporting arm or girder I2. The arrester is indicated generally at I3, 'and is connected in a high resistance electrical path between the transmission line I0 and ground, this path including a spark gap comprising spaced electrodes I4 and a metal pipe or conduit I5. 'Ihe pipe I5. is grounded as indicated in the drawing by conductor I6 and is mounted on a suitable support I1 by means of brackets at both ends and communicating with the interior of the arrester I3, as described more fully hereinafter.

The portion of the arresting device I3 in which the arc is formed during discharge is illustrated as consisting of a substantially cylindrical tube 2| of molded phenolic condensation product or other insulating material having an inner liner or shell 22 of fibrous material. The tube 2I is open -at each end and is supported in metal ferrulesv 23 and 24 adjacent its upper and lower ends, respectively. The lower end of the ferrule 24 is threaded as indicated at 25 for connection to the pipe I5 through a suitable metal reducing coupling 26 whereby the device I3 may be adequately supported and grounded. 'Ihe coupling 26 also forms an electrode at the lower end of the discharge chamber, A metal electrode, or anode 2l comprising an elongated cylindrical portion having an opening 28 therethrough extends downwardly in a tightly fitting relation within the upper end of the ber liner 22. 'I'he upper end of the electrode 2l is provided with a head 29 having a shoulder 3l) abutting against the upper ends of the tube 2| and the liner 22. 'Ihe outer surface of the lower end of the elec- .trode is provided with circumferentially extending serrations such as are shown at 3l in the enlarged fragmentary view of Fig. 3 to increase I9, this pipe being open the turbulency of thegas forced between the ilber tube and the lower end or the electrode. This effectively prevents a rise in pressure between the end of the ilber tube and the electrode head and eliminates stress betweenl the tubes and the rerrule 23.

It will now be appreciated4 that the tube 2l and the inner shell 22'constitute a chamber of elongated shape in which a discharge may occur between the upper electrode 21 and lower electrode 23 upon the application of electrical energy of sufiicient voltage and frequency thereto, and while it is found convenient to construct this chamber of tubular shapeto facilitate manufacture ofthe device and' reduce'the oost of materials. the precise shape ci the chamber is not of major importance.

If the interior walls of this chamber fare coated with conducting material, for instance an aluminum powder, the resistance of the path between the anode 21 and the pipell will be mate riallyl reduced an'd the formation. of an arc be tween these conductors will be facilitated. I'he heat of this arc, however, will';-rapidly vaporlze the conducting coating, thus materiallyincreaeing the resistance between -the conductors, and the heated gas including the vapors of the coating will be expelled violently from the lowerend of the chamberand through the pipe I5l to a point adjacent the groundwherethey-are exhausted harmlessly. this expulsion'- of gas serving to blow out or extinguish the arc formed within the chamber. It will -be understood that the opening of the circuit is "facilitatedby the destruction of the conducting 4'coa'.ting and the consequent.l increase in electrical resistance of the path `between the anode 21 an'd the pipe I5.

-The ferrule 23 is threaded at its upper end to receive .a coupling member 33 which in turn is threaded onto the lower end of the baille member 34. The uppersurface of the anode head 23 is recessed defining-,a chamber 32 and the outer` rim of the anode head- 23issecurely clamped by the coupling 33 between'the upperend of the ferrule 23 and the lower end of the baille member 34.

The baille member 34, as is more clearly illustrated in Figs. 4 and 5, ,is provided at its lower end with a recessed expansion chamber 35, conical in shape at its upper extremity, and which chamber is in .central alignment with the passage 23 through the anode 21. The upper end of the baille member. 34- is provided with a conical recess- 33, while a plurality 'of circumferentially arranged tubular passages 3 1 extend longitudinally through the balllemember 34 communicating between the chamber 32 and the recess 33. From the lowermost portion of the recess 33 a plurality of radially extending and downwardly sloping passages 33 are provided for reasons which will become obvious as the descriptiori proceeds. The outer ends of the passages 33 communicate with passages 31.

The upper end of the baille member 34 is threaded into the lower end of a coupling member 4I, the upper end of the coupling' member 4I being in turn threaded to a flanged portion between Va suitable shoulder 53 provided in the 42 of the reservoir head 43. The upper end of the reservoir 44 is normally closed by means of a cap 45 which is threaded thereon as indicated at 43, a washer 41 being provided between the cap and the reservoir to effectively seal the latter. V

The upper portion of the cap 45 is provided with a boss 43 having a threaded aperture 49 innersuriace of ilange 42 and the shoulder 53 of coupling member 4I.

Communicating between the chamber 53 and theinterior of the reservoir 44 is a cylinder 3| prvidedwith a plurality of inwardly eitending lugs.32.which serve as guide means for a reciprocatingvalve stem 33. At its upper end the valvestenr- 33 is provided with an adiustable .valve head 34 cooperating with a suitable seat formed at the lower end of the reservoir. At its -lower end the valve stem is provided with a valve -head 35 which isdesvigned for cooperation with A a suitable seat formed at the lower end of the cylinder 3l.

It will thus be seen that the valve stem 33 la supported forfree vertical sliding movement in the guide 1118s, and when in the lower position as shown in Fig. 2 of the drawing, the valve head 34 engages `with its seat to seal the lower end of the reservoir 44. When the valve stem 33 is raised to engage the valve head 35 with its valve seat, coating material may ilow out of the reservoir 44 -andbetween the lugs 32 substantially illllng the cylinder 3|. When the valvestem'33 now drops to the lower position in which it is shown in Fig. 2, the coating material collected in the cylinder will flow downwardly into the iunnel chamber 53 through openings 55 and 52 into the conical recess 33 of the baille member 34. From the conical recess 33 the material will flow downwardly through the sloping passages 33 and passages 31 into the chamber 32 and through the anode opening 23 into the discharge chamber defined by the ber liner 22. In passing through thedischarge chamber the powdered material will lodge principally on the surface of theflber liner 22 reconditioning the varrester for a subsequent operation and any excess material will ow on through the pipe I5 to the ground.

The operation of the device will now be apparent. Upon the occurrence of an abnormal con- -dition on the power line I3, such as the setting up of a high voltage disturbance thereon as the result of a ilash of lightning or other abnormal voltage, a discharge will be eilected across the external arc gap I4 and through the metal parts of the device I3 to the anode 21. I'he current will continue to ilow readily between the anode 21 and the grounded pipe I5 by reason of the deposit of conductive coating, for instance powdered aluminum, on the ilbrous liner 22. As the result of the heat developed by the current, the conductive coating will be valporized and the heated air, gas, or vapor will be forcibly'expelled from the lower end of the device I3 into the pipe I5 to a point adjacent the ground as hereinbefore explained.

The pressure developed in the arcing chamber will be communicated through the anode opening 23, the passages 31 in the baille member 34, the openings 52 and 55, to the funnel chamber the device, the valve stem 63 will fall to its initial position, and the fresh supply of coating will be discharged downwardly through the funnel chamber 56 as hereinbefore described and upon the walls of the fiber liner 22 reconditioning the latter for the next discharge.

It will be understood that during and immediately subsequent to a high capacity discharge, the gas pressure at the lower end of the anode 21 is many thousand pounds per square inch and the temperature is momentarily that of the electric arc. The 'high temperature gas jet flowing upwardly through the relatively narrow opening 28 in the anode will be somewhat throttled thereby and in emerging from the upper end of the opening will expand in the chambers 32 and 35. 'I'he temperature of the gas jet will be cooled considerably due to the expansion thereof and in impinging upon the relatively cool surfaces deining the expansion chamber 35. After striking the upper end of the chamber 35 the gas will flow downwardly along the side walls into the chamber 32 and then upwardly through the passages 3l, 38, 52, 55 into the funnel chamber 56 where further expansion of the gas and further cooling thereof will take place. Due to the successive throttling, expanding and baffling of the gas, the pressure rise in the funnel chamber 56 will be relatively slow so that the motion of the valve assembly resulting from this pressure increase is suiciently slow to prevent overstressing of any part thereof. It will be understood of course that before the valve head 65 can be moved to the closed position, a certain amount of gas will pass into the cylinder 6I and upon the opening of the-valve 64, this gas will pass on into the reservoir 44. The gas entering into the reservoir 44 will be of a relatively low temperature, that is, materially below the melting point of the stored powder.

Due to the relatively long path taken by the powder discharged from the cylinder 6I to the discharge chamber, ample time exists for all of the extremely hot gases to be cleared from the expansion chamber before the powder reaches it, so that the reconditioning powder will not be immediately vaporized.

It will be observed that the arrangement described is of a relatively simple nature, i; light and readily constructed, andmay be quickly installedl in any protective system. The occurrence of an abnormal condition in the line is readily detected by the ilash of a discharge through the lower end of the device so that any necessary steps to correct the condition may be taken promptly. Having described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that I do not wish to be limited thereto, since many modications may be -made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim: as newand desire to secure by Letters Patent of the United States is:

1. In an electric protective device, the combination of a discharge chamber having a pair of spaced electrodes associated therewith, said chamber having a portion receiving a finely divided conducting coating disposedl in the electrical path between the electrodes and destructible when heated, a reservoir constituting a source of supply of such coating, a valve for controlling the supply of coating from said reservoir to said chamber, an opening communicating with said discharge chamber, a bailiing member having an I expansion chamber disposed over said opening, and passages through said bailling member communicating between said valve and said opening.

2. In a lightning arrester of the type having a discharge chamber adapted to be automatically reconditioned following an electrical discharge therethrough by finely divided material from a quantity thereof in a reservoir positioned in the upper part of said lightning arrester, the com:- bination of a valve operable by pressure generated in said discharge chamber .for passing a portion of the material in said reservoir to said discharge chamber, a. passage extending between said discharge chamber and said valve, baffling means including an expansion chamber arranged in said passage whereby said valve is protected against the direct force of the pressure gases generated in said discharge chamber.

3. In an electric protective device, thecombination of a discharge chamber having a pair ofspaced electrodes therein, said chamber having a portion for receivinga finely divided conducting coating disposed in the electrical path between said electrodes and destructible when heated, a reservoir constituting a source of supply for such coating, a valve for controlling the supply of coating from said reservoir to said chamber, a passage through one of said electrodes for material passing from said reservoir to said chamber, a member arranged between said one electrode and said reservoir having an expansion chamber in alignment` with said passage,

ilowing from said reservoir to said chamber.

HERMAN B. WOLF. 

